Zilog z80 to Motorola 6809 Transcode – Part 018 – Transcode is complete and a look at level 256

Hello again,

I’ve transcoded all the Pac Man z80 code to the 6809 now, except for some audio related code which isn’t going to be used on the CoCo 3.  The game plays properly now.  The demo mode ghost movement matches the original Pac Man ghost movement so I think it should play the same as the real machine meaning you should be able to use Pac Man patterns on the CoCo 3 version just like the real hardware.

The cutscenes are coded in but they currently look pretty bad right now since the sprites are changed around for normal game mode and the cutscenes use different sprites that I had to remove for normal game play (space limitation).  So I have to work on cleaning up the cutscenes.  Other then that any other little graphic glitch is sprite related and I don’t know if I’m going to fix them up before working out a better way to render the sprites which may fix those little glitches…

I tested out the game and changed the level to 256 to see if it would be drawn crazy just like a real Pac Man machine does and I’m happy to say that it does.  The only difference is the colour of the text isn’t the same, this is because the palette info on Pac Man hardware is handled differently then the CoCo 3.



So from this point to make Pac Man perfect I need to:

  • Fix sprites while playing cutscene animations
  • Add Joystick support (I don’t have a joystick for my CoCo 3)
  • Speed up the game
  • Add sound output

Because the screen is a little too tall to be shown on the CoCo 3 screen I have written some code that auto scrolls vertically showing as much of the maze as it can at all times.  You can press the A key to see the top of the screen where the scores are shown.  Or you can press Z to see the bottom of the screen where the level info and the number of lives is shown.

See you in the next post…

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